I. Field of the Invention
The present invention relates generally to fluid dispensing mechanisms and, more particularly, to a self-aligning positive displacement dispenser.
Sealants and adhesives, especially of the high viscosity type, are oftentimes difficult to dispense in an accurate and controlled manner. Excessive amounts of dispensed material are wasteful and give a sloppy appearance while insufficient amounts could affect the sealing quality. Moreover, the dispensing should be carried out quickly without compromising accuracy. II. Description of the Prior Art
There are a number of known designs for dispensing fluids such as adhesives, sealants, and the like, at accurately controlled flow rates, in accurate quantities, and for accurate placement on a receiving surface.
The commonly assigned U.S. Pat. No. 4,347,806 to Argazzi et al issued Sept. 7, 1982 and entitled "Liquid Dispensing Apparatus" discloses a positive displacement type of valve in which a quantity of the fluid is admitted into a chamber whereupon a piston then forces that quantity of fluid out through the dispensing outlet or nozzle. In this instance, and in other known instances of the prior art, piston alignment problems result in premature wear of the moving components, seal leakage problems, poor performance and reliability.
It is noteworthy that loss of the fluid that does not issue from the outlet nozzle but instead finds its way into other cavities of the dispensing mechanism is not the primary concern. Rather, when the fluid is a sealant or adhesive material, it subsequently accumulates, then hardens, and thereby has a detrimental effect on the operation of the dispensing mechanism, even to the point of rendering it inoperative.
A significant improvement in the state of the art occurred with the inventions disclosed in the following co-pending and commonly assigned applications: Ser. No. 57,614 filed June 3, 1987, Ser. No. 176,875 filed Apr. 4, 1988 and Ser. No. 176,877 filed Apr. 4, 1988 which are hereby incorporated by reference in their entirety. While not a positive displacement pump, the invention of Ser. No. 57,614 relates to a simplified fluid dispenser for dispensing precise quantities of fluid without requiring special seals or springs. It comprises a housing defining a fluid reservoir having an inlet for delivery of pressurized fluid to the reservoir, and including a valve seat defining an outlet for dispensing fluid from the reservoir. A deformable end cap overlies an open end of the housing opposite the outlet and normally biases a valve engageable with the valve seat to the closed position. The valve is opened by an opening force applied by way of a valve stem against the bias of the end cap. It is able to dispense fluids having an extremely broad range of viscosities, namely, from one centipoise to a value substantially in excess of one million centipoises.
Furthermore, the dispenser of that invention can be turned on and off instantaneously, that is, starting and stopping the flow of fluid occurs at substantially the same time as operation of the valve actuator. Another significant feature of that invention resides in its construction and manner of operation according to which movement of an actuator used to operate the dispenser causes simultaneous and equal movement of the valve off its seat for dispensing the fluid. This feature allows the dispenser to operate at very high actuation speeds. In actuality, the dispensing of the fluid is substantially simultaneous with the actuation of the valve and continues while the valve remains open.
Ser. No. 176,877 relates to a sealless modular dispenser while Ser. No. 176,875 discloses a sealless modular positive displacement dispenser, which is a significant improvement over the device disclosed in Ser. No. 57,614. However, there is no provision for self-alignment of the dispensing piston in the fluid reservoir with the result that the aforementioned problems associated with piston misalignment are not overcome.
It is an object of the present invention to provide a reservoir design which provides for self alignment of an associated piston in a positive displacement dispenser to thereby reduce premature wear of the moving components and improve the performance and reliability of the dispensing apparatus.
It is a further object of the present invention to provide a simplified interconnection between the piston and the means for reciprocating that piston which accommodates anticipated misalignment between these.